JP2003070249A - Switching power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the efficiency of a switching power supply device having a power factor improving function. SOLUTION: This switching power supply device has a rectifying circuit 4 connected to a pair of AC power terminals 1, 2; a main switch Q1 connected between a pair of rectification output conductors 43, 45 of the rectifying circuit 4 via a main inductor L1 , an inverse current blocking diode D5 , and a part N1b of the primary winding N1 of a transformer 5; a smoothing capacitor C1 connected in parallel with a series circuit of the primary winding N1 and the main switch Q1 ; the secondary winding N2 of the transformer; a rectifying smoothing circuit 6; and an auxiliary circuit 7. The auxiliary circuit 7 comprises a series circuit of an auxiliary winding N3 , an auxiliary diode Da , and an auxiliary switch Q2 . This series circuit is connected in parallel with the series circuit of the primary winding N1 and the main switch Q1 . The auxiliary circuit 7 contributes to ZVS (Zero Voltage Switching) of the main switch Q1 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device capable of improving power factor and waveform.

[0002]

2. Description of the Related Art AC-to-DC conversion can be performed by a rectifying / smoothing circuit including a diode rectifying circuit connected to an AC power source and a smoothing capacitor connected to the rectifying circuit. However, the charging current of the smoothing capacitor flows only in the peak region of the sinusoidal AC voltage. Therefore, the power factor at the AC input terminal of the diode rectifier circuit is poor.
Moreover, the DC voltage cannot be adjusted only by the diode rectifier circuit.

A switching power supply device for solving the above-mentioned drawbacks of the rectifying / smoothing circuit is disclosed in Japanese Patent Application Laid-Open No. 8-154379. The switching power supply device disclosed herein includes a rectifier circuit, a smoothing capacitor, and a DC-
It has a DC converter circuit and an inductor or reactor for power factor improvement. When the switch of the DC-DC converter circuit is turned on, the inductor is connected between the pair of output terminals of the rectifier circuit via the switch, and a current flows there. Since the amplitude of the current flowing through the inductor changes according to the change in the amplitude of the AC voltage, the power factor and the waveform of the AC input current are improved.

[0004]

By the way, there is a demand for reduction of power loss, that is, improvement of efficiency of a switching power supply device having a power factor improving function and a waveform improving function.

Therefore, an object of the present invention is to provide a switching power supply device capable of achieving power factor improvement, waveform improvement and efficiency improvement with a relatively simple structure.

[0006]

The present invention for solving the above problems and achieving the above objects will be described with reference to the reference numerals of the drawings showing the embodiments. However, the reference numerals here are for helping understanding of the present invention, but do not limit the present invention. A switching power supply device for converting an AC voltage supplied from an AC power supply of the present invention into a DC voltage includes a first and a second AC input terminal (1, 2) for supplying an AC voltage, and the first And a second rectification circuit (4 or 4) connected to the second AC input terminals (1, 2) and having first and second rectification output conductors (43, 45)
a), a transformer (5 or 5a or 5b or 5c) having a main winding (N1) and an auxiliary winding (N3) electromagnetically coupled to the main winding (N1), and the main winding (N1) ) And a smoothing capacitor (C1) connected between the second rectified output conductor (45) and one end connected to the first rectified output conductor (43), and at least the main winding. The smoothing capacitor (C1) through a part of the line (N1)
A main inductor (L1) having the other end connected to
A main switch (Q1) connected between the other end of the main winding (N1) and the second rectified output conductor (45), and a capacitor or parasitic connected in parallel to the main switch (Q1). A soft switching capacitance means (Cq1) comprising a capacitor, a rectifying / smoothing circuit (6) connected to the transformer (5 or 5a or 5b or 5c) to obtain a DC output voltage, and the soft switching capacitance means ( At least the auxiliary winding (N3) in order to supply the auxiliary winding (N3) with a current capable of generating a voltage in the main winding (N1) for enabling the discharge of Cq1). Through an auxiliary switch (Q2) connected in parallel to the smoothing capacitor (C1), the main switch (Q1) and the auxiliary switch (Q2), and the AC input terminal A first function of controlling ON / OFF of the main switch (Q1) at a repetition frequency higher than the frequency of the AC voltage applied to the child (1, 2), and the main switch when the main switch (Q1) is turned on. In order to soft-switch (Q1), the ON control of the auxiliary switch (Q2) is started at a time point (t1) prior to the start time point (t2) of the ON control of the main switch (Q1), and the main switch (Q2) is started. At the end of turning on Q1) (t5
) Or the time (t4) before the end time (t5)
.About.t5), a control circuit (8) having a second function of terminating the ON control of the auxiliary switch (Q2).

According to a second aspect of the invention, a series circuit of the auxiliary winding (N3) and the auxiliary switch (Q2) is used for smoothing through at least a part of the main winding (N1). It can be connected in parallel with the capacitor (C1). In addition, as described in claim 3, further comprising an auxiliary diode (Da) connected in series to the auxiliary winding (N3) and the auxiliary switch (Q2) to prevent backflow. Is desirable. Further, as described in claim 4, the rectifier circuit (4 or 4a) is further provided.
From the auxiliary rectification output conductor (44) for outputting substantially the same rectification voltage as the first rectification output conductor (43)
And the auxiliary rectifying output conductor (44) and one end of the smoothing capacitor (C1) electromagnetically coupled to the main winding (N1) to obtain a voltage for charging the smoothing capacitor (C1). Auxiliary winding for charging (N
4) and are desirable. Further, as described in claim 5, an auxiliary inductor (L2) having one end connected to the auxiliary rectification output conductor (44), the other end of the auxiliary inductor (L2) and the auxiliary charging winding. (N
4) Auxiliary capacitor for charging (C2) connected between
And a charging auxiliary diode (D6) connected in parallel with the series circuit of the charging auxiliary winding (N4) and the charging auxiliary capacitor (C2). Further, as described in claim 6, further, an auxiliary inductor (L2) whose one end is connected to the auxiliary rectifying output conductor (44), the other end of the auxiliary inductor (L2) and the auxiliary charging winding. (N4) is connected to the auxiliary charging diode (D6) and the auxiliary charging winding (N4)
) And the auxiliary charging diode (D6) connected in parallel to the series circuit of the auxiliary charging capacitor (C2
) And are desirable. Further, as set forth in claim 7, it further comprises a reverse current blocking auxiliary diode (D7) connected between the auxiliary rectifying output conductor (44) and the charging auxiliary winding (N4). Is desirable. Further, as described in claim 8, it is preferable that the auxiliary inductor (L2) further includes a reverse current blocking diode (D7) connected in series. Further, as shown in claim 9, it is preferable that the backflow prevention diode (D5) is further connected in series to the main inductor (L1). The rectifier circuit (4) further includes a first electrode connected to the first AC input terminal (1), the first rectified output conductor (43), and an auxiliary rectifier. A first diode (D1) having a second electrode respectively connected to the output conductor (44)
) And a second electrode (2) having an electrode connected to the second rectified output conductor (45) and a second electrode connected to the first AC input terminal (1). D2
), And a first electrode connected to the second AC input terminal (2) and a second electrode connected to the first rectified output conductor (43) and the auxiliary rectified output conductor (44), respectively. A third diode (D3) having a first electrode connected to the second rectified output conductor (45) and a second electrode connected to the second AC input terminal (2). And a fourth diode (D4) having The rectifier circuit (4) is connected to a first electrode connected to the first AC input terminal (1) and the first rectified output conductor (43). A first diode (D1) having a second electrode
And a first connected to the second rectified output conductor (45)
Second diode (D2) having a second electrode connected to the first AC input terminal (1) and a first diode connected to the second AC input terminal (2). A third diode (D3) having an electrode and a second electrode connected to the first rectified output conductor (43), and a first electrode connected to the second rectified output conductor (45) And the second
A fourth diode (D4) having a second electrode connected to the AC input terminal (2), a first electrode connected to the first AC input terminal (1) and the auxiliary rectified output A fifth diode (D11) having a second electrode connected to the conductor (44), a first electrode connected to the second AC input terminal (2) and the auxiliary rectification output conductor (44). )
And a sixth diode (D12) having a second electrode connected to. In addition, claim 12
, The main inductor (L1)
Between the rectified output conductor (43) and the tap (10) of the main winding (N1). Further, as set forth in claim 13, the main inductor (L1) is connected to the first rectified output conductor (43) and the main switch (Q1).
It is possible to connect between and without the main winding (N1).

[0008]

The invention of each claim has the following effects. (1) Current flows through the main inductor (L1) during the ON period of the main switch (Q1), and this main inductor (L1)
) The current amplitude is proportional to the AC voltage amplitude. Therefore, the power factor and the waveform of the switching power supply device are improved. (2) When the auxiliary switch (Q2) is turned on, a current flows through the auxiliary winding (N3). As a result, the main winding (N
The voltage of 1) changes to a state allowing discharge of the soft switching capacitance means (Cq1), the soft switching capacitance means (Cq1) discharges, and the voltage between both terminals of the main switch (Q1) decreases. Main switch (Q
When the main switch (Q1) is turned on while the voltage of 1) is lowered, soft switching or zero voltage switching (ZVS) of the main switch (Q1) is achieved, and switching loss and noise are reduced. (3) The main switch (Q1) is used both for turning on / off the voltage for power factor improvement and waveform improvement, and for turning on / off the voltage for DC-DC conversion. Therefore, it is possible to reduce the size and cost of the switching power supply device capable of improving the power factor and the waveform. (4) Since the auxiliary winding (N3) for soft switching the main switch (Q1) is included in the transformer (5-5e) together with the main winding (N1), it is possible to downsize the switching power supply device. Become. According to the inventions of claims 2 and 3, the supply of current to the auxiliary winding (N3) can be easily achieved with a simple circuit. According to the inventions of claims 4 to 11, the following effects can be obtained. (1) to be charged to a desired value the smoothing capacitor (C1) by the main inductor (L1) to the flowing current (I _L1) and smaller also the auxiliary charging circuit (30) for improving the power factor and waveform improvement You can That is, the smoothing capacitor (C1) is the power factor improving and waveform improving inductor (L1
) And a second charging path through the auxiliary charging circuit (30 or 30a or 30b or 30c). Therefore, as compared with the case where the charging current of the smoothing capacitor (C1) is supplied only through the first charging path, when the charging current is supplied through the first and second charging paths according to the present invention, The charging current of the first charging path can be reduced by the current value of the charging path. Therefore, the power loss in the main inductor (L1) included in the first charging path is reduced, and the efficiency of the switching power supply device is improved. Further, the external dimensions of the main inductor (L1) can be reduced. (2) The charging voltage of the smoothing capacitor (C1) can be increased with the help of an auxiliary charging circuit (30 or 30a or 30b or 30c). Smoothing capacitor (C
When the charging voltage of 1) becomes high, the main inductor (L1) of the first charging path will be at or near the peak value of the input AC voltage.
It is possible to prevent an excessive current from flowing into the smoothing capacitor (C1) through. As a result, the harmonic component of the AC input current can be reduced. (3) The auxiliary charging circuit is a charging auxiliary winding (N4) electromagnetically coupled to the main winding (N1) of the transformer (5b or 5c).
The auxiliary charging circuit (30 or 30a or 30
The configuration of b or 30c) is simple and compact. Claim 5
According to the inventions 6 and 6, it is possible to easily smooth the current flowing through the auxiliary charging circuit. According to the invention of claim 12, the input voltage of the main inductor (L1) is the tap (1
Current flows in the main inductor (L1) only when it is higher than the voltage of (0). Therefore, the power loss in the main inductor (L1) is reduced, and the efficiency of the switching power supply device is increased. According to the invention of claim 13, the current flowing through the main inductor (L1) is not limited by the main winding (N1). Therefore, sufficient current for power factor improvement and waveform improvement can be passed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, first to fourteenth embodiments of the present invention will be described with reference to FIGS. It should be noted that portions common to each of the embodiments are denoted by the same reference numerals and will be described in detail in any one of the embodiments, and description thereof will be omitted in another embodiment.

[0010]

[First Embodiment] A switching power supply device according to a first embodiment shown in FIG. 1 includes first and second AC input terminals 1 and 2.
, Noise removal filter 3, and bridge rectifier circuit 4
, Main inductor L1, smoothing capacitor C1, transformer 5, main switch Q1, snubber or ZVS
Soft switching capacitor Cq1 which can also be referred to as (zero volt switching) or resonance
And the first and second parallel diodes Dq1 and Dq2, the rectifying / smoothing circuit 6, the soft switching auxiliary circuit 7 according to the present invention, and the control circuit 8.

The first and second AC input terminals 1 and 2 are connected to a commercial AC power source for supplying a 50 Hz sinusoidal AC voltage, for example. First and second AC input terminals 1,
The noise removing filter 3 connected between the rectifier circuit 2 and the rectifying circuit 4 is a well-known circuit including a plurality of inductors and a plurality of capacitors, and removes a high frequency current component.

The rectifying circuit 4 has first and second AC input conductors 41 and 42, a first rectifying output conductor 43, a second rectifying output conductor 45, and first and second electrodes, respectively. The first, second, third and fourth diodes D1, D2,
It consists of D3 and D4. First and second AC input conductor 4
Reference numerals 1 and 42 are connected to the first and second AC input terminals 1 and 2 via the filter 3. The first electrode or anode of the first diode D1 is connected to the first AC input conductor 41, the second electrode or cathode of the second diode D2 is connected to the first AC input conductor 41, and the third The first electrode (anode) of the diode D3 is connected to the second AC input conductor 42, and the second electrode (cathode) of the fourth diode D4 is connected to the second AC input conductor 42. And the second electrodes (cathodes) of the third diodes D1 and D3 are connected to each other, and the interconnection point 48 is connected to the first rectified output conductor 43. The anodes of the second and fourth diodes D2, D4 are connected to each other, the interconnection point 49 of which is connected to the second rectified output conductor 45. In the following, the second rectified output conductor 45 may be referred to as a ground side rectified output conductor or a common rectified output conductor.

The transformer 5 comprises a magnetic core 9, a primary winding N1 as a main winding, a secondary winding N2 as an output winding, and a tertiary winding N3 as an auxiliary winding for soft switching according to the present invention. Have and. The primary winding N1, the secondary winding N2, and the tertiary winding N3 are wound around the magnetic core 9 and electromagnetically coupled to each other. The primary winding N1 as a main winding has a tap 10 and is divided into first and second portions N1a and N1b. The polarities of the primary winding N1, the secondary winding N2, and the tertiary winding N3 are set as shown by black circles. Primary winding N
The 1 and the secondary winding N2 have opposite polarities.

The smoothing capacitor C1 which is an electrolytic capacitor is connected between one end of the primary winding N1 and the second rectified output conductor 45. One end of the main inductor L1 is the first
Of the main inductor L1 and the other end of the main inductor L1 is connected to the tap 10 of the primary winding N1. Therefore, the other end of the main inductor L1 is at least the primary winding N1.
Is connected to one end of the smoothing capacitor C1 via the first portion N1a. The position of the tap 10 of the primary winding N1 for connecting the main inductor L1 can be arbitrarily changed. When the ratio of the second portion N1b to the first portion N1a of the primary winding N1 is increased, the efficiency of the switching power supply device is improved, but conversely the effect of power factor improvement is reduced.

The main switch Q1 consisting of an insulated gate field effect transistor is connected between the other end of the primary winding N1 and the second rectified output winding 45. The main switch Q1 is connected in parallel to the smoothing capacitor C1 via the primary winding N1.

A soft-switching capacitor Cq1 as a soft-switching capacitance means is connected in parallel with the main switch Q1 and has a capacitance value sufficiently smaller than that of the smoothing capacitor C1. Although this soft switching capacitor Cq1 is shown as an individual capacitor in FIG. 1, it can be replaced by a parasitic capacitance between two main electrodes of the main switch Q1, that is, a drain-source.

The parallel diode Dq1 having a protective function for the main switch Q1 is connected in reverse parallel to the main switch Q1. Although the parallel diode Dq1 is shown as an individual diode in FIG. 1, it can be replaced with a built-in diode called a body diode of the main switch Q1.

The rectifying / smoothing circuit 6 connected to the secondary winding N2 of the transformer 5 comprises a rectifying diode Do and a smoothing capacitor Co. The smoothing capacitor Co is a diode D
It is connected in parallel to the secondary winding N2 via o. The diode Do has a direction in which it is turned off when the switch Q1 is on and turned on when the main switch Q1 is off.
A pair of output terminals 11 connected to the smoothing capacitor Co,
A DC output voltage is obtained between 12 and is supplied to the load 20.

The soft switching auxiliary circuit 7, which can also be called a resonance auxiliary circuit, includes a tertiary winding N3 as an auxiliary winding, an auxiliary switch Q2, an auxiliary diode Da, and a second parallel diode Dq2. ..

The tertiary winding N3 is electromagnetically coupled to the primary winding N1 and the secondary winding N2. The polarity of the tertiary winding N3 depends on the current flowing through the primary winding N3 to generate a voltage for enabling the soft switching capacitor Cq1 to discharge.
1 is set so that it can be generated. The tertiary winding N3 has a leakage inductance La. An individual inductor can be connected in series with the tertiary winding N3 when the leakage inductance of the tertiary winding N3 makes it impossible to obtain all the required inductance La.

The series circuit of the tertiary winding N3, the backflow prevention auxiliary diode Da and the auxiliary switch Q2 is connected in parallel to the smoothing capacitor C1. The series circuit of the auxiliary circuit 7 is connected in parallel to the series circuit of the primary winding N1 and the main switch Q1. The auxiliary switch Q2 composed of an FET has a built-in parallel diode Dq2 having a directivity in which a reverse current flows. Although not shown, the auxiliary switch Q2 has a parasitic capacitance between its drain and source. The auxiliary diode Da has a directionality in which it is forward-biased by a voltage induced in the tertiary winding N3 while the main switch Q1 is off.

The switch control circuit 8 uses the conductors 13 and 14 to detect the output voltage Vo.
1 and 12 and by a conductor 15 to the control terminal of the main switch Q1 and by a conductor 16 to the control terminal of the auxiliary switch Q2. The control circuit 8 and the sources of the two switches Q1 and Q2 are also electrically connected, but not shown.
The control circuit 8 forms a first control signal Vg1 for turning on / off the main switch Q1 and a second control signal Vg2 for turning on / off the auxiliary switch Q2.

As shown in FIG. 2, the control circuit 8 of FIG. 1 includes a voltage detection circuit 21, an error amplifier 22, and a reference voltage source 23.
A sawtooth wave generator 24, a first comparator 25, a level adjusting voltage source 26, and a second comparator 27. The voltage detection circuit 21 is connected to the output terminals 11 and 12 of FIG. 1 by the conductors 13 and 14 and sends the detected value of the output voltage Vo to the error amplifier 22. The error amplifier 22 sends an error voltage Vr1 corresponding to the difference between the detected value and the reference voltage of the reference voltage source 23 to the first comparator 25. The output of the error amplifier 22 can be sent to the comparator 25 and the level setting circuit 26 using a known photo coupler. In addition, the voltage detection circuit 2
It is also possible to couple 1 and the error amplifier 22 with a photocoupler. The first comparator 25 receives the error voltage Vr1 and the sawtooth wave generator 2
The sawtooth wave Vt of FIG. 4 is compared as shown in FIG.
It is formed as shown in FIGS. The first control signal Vg1 is sent by conductor 15 to the gate of the main switch Q1. The voltage source 26 for level adjustment is a DC voltage -Vd.
And a voltage Vr2 lower than the output voltage Vr1 of the error amplifier 22 by Vd. The second comparator 27 compares the sawtooth wave Vt of the sawtooth wave generator 24 and the voltage Vr2 on the output side of the level adjusting voltage source 26 as shown in FIG. The second control signal Vg2 consisting of a pulse slightly wider than the PWM pulse is shown in FIG. 4 (B) and FIG.
It is formed as shown in (C) and is sent by conductor 16 to the gate of auxiliary switch Q2.

As shown in FIG. 4B, the auxiliary switch Q2
The second control signal Vg2 for switching from the low level to the high level during the off period of the main switch Q1, for example, at time t1 in FIG. 4, starts the on control of the auxiliary switch Q2. As shown in FIG. 4A, the first control signal Vg1 for the main switch Q1 is the time t1 at which the ON control of the auxiliary switch Q2 is started.
At a time t2 which is a little later than the above, the low level is changed to the high level and the ON control of the main switch Q1 is started. The time width from the ON control start time t1 of the auxiliary switch Q2 to the ON control start time t2 of the main switch Q1 is the main switch Q1.
Is determined so that the switching loss during the turn-on operation can be reduced. In this embodiment, the end time of the ON period of the auxiliary switch Q2 is the time t5 in FIGS. 4 and 5, which is the same as the ON end time of the main switch Q1. However, the ON end time of the auxiliary switch Q2 can be changed to an arbitrary time between the time t4 in FIG. 4 and the ON end time t5 when the current Iq2 of the auxiliary switch Q2 becomes zero. That is, the ON end time of the auxiliary switch Q2 is determined to be the ON end time t5 of the main switch Q1 at the latest.
When the turning-on end time of the auxiliary switch Q2 is changed to t4 time as shown by the dotted line in FIG. 4 (B), for example, the monomultivibrator is shown at the output terminal of the second comparator 27 in FIG. 2 as shown by the dotted line. (MMV) 28 is connected and this M
The MV 28 may form pulses of t1 to t4 in FIG. 4, for example.

[0025]

[Operation] When the first and second AC input terminals 1 and 2 are connected to an AC power supply and the main switch Q1 is turned on and off,
The smoothing capacitor C1 is charged to a desired DC voltage Vc1. The operation of the circuit of FIGS. 1 and 2 in the normal state where the smoothing capacitor C1 is charged to the voltage Vc1 is shown in FIGS.
Will be described with reference to. FIG. 3 schematically shows the state of each part of FIG. 1 for explaining the power factor improvement and the waveform improvement. The main switch Q1 is schematically shown in FIG. 3A in a state where the sinusoidal AC voltage Vac of 50 Hz shown in FIG. 3E is supplied between the first and second AC input terminals 1 and 2. When the on / off control is performed by the first control signal Vg1 having a repetition frequency of, for example, 20 kHz, the current Iq1 of the main switch Q1 shown in FIG. 3C and the output current I4 of the rectifying circuit 4 shown in FIG. The amplitude or peak value is the AC voltage Vac
Changes according to the amplitude of. As a result, the AC input current Iac shown in FIG. 3D approximates to a sine wave, and the power factor and waveform are improved. Since the main inductor L1 is connected to the tap 10 of the primary winding N1, the smoothing capacitor C1
The current IL1 does not flow through the main inductor L1 unless the rectified output voltage V4 becomes higher than the voltage of the tap 10 given by the voltage Vc1. In FIG. 3, t1 to t6 period and t8
The rectified output current I4 and the AC input current Iac are flowing during the period from to t9.

The operation of the main circuit portion excluding the auxiliary circuit 7 of FIG. 1 will be described in more detail. For example, during the ON period Ton of the main switch Q1 shown at t2 to t3 in FIG. 3, a current flows through the rectifier circuit 4, the main inductor L1, the second portion N1b of the primary winding N1, and the main switch Q1. At the same time, current also flows in the path of the smoothing capacitor C1, the primary winding N1, and the main switch Q1. Secondary winding N during this ON period Ton
Since the voltage generated at 2 has the direction to reverse-bias the diode Do, the diode Do is kept non-conductive. As a result, energy is stored in the transformer 5 during this ON period Ton. Energy is also stored in the main inductor L1. Off period Tof shown from t3 to t5 in FIG.
When the main switch Q1 is turned off at f, the stored energy of the main inductor L1 and the transformer 5 is released, and the path of the rectifier circuit 4, the main inductor L1, the first portion N1a of the primary winding N1 and the smoothing capacitor C1 is released. A current I4 flows through the capacitor, and the smoothing capacitor C1 is charged. This current I4
Decreases with time and becomes zero at time t4 in FIG. During this off period Toff, a voltage in the direction of turning on the diode Do is induced, and power is supplied to the capacitor Co and the load 13 via the diode Do. T in FIG.
When the main switch Q1 is turned on again at the time point 5, t2 to t
The same operation as in 5 periods is repeated. Capacitor Co
When the voltage Vo becomes higher than the reference value, the ON period of the main switch Q1 is shortened, the energy stored in the transformer 5 is reduced, and the output voltage Vo is returned to the reference value. When the output voltage Vo becomes lower than the reference value, the main switch Q
The ON period of 1 becomes longer, the accumulated energy of the transformer 5 increases, and the output voltage Vo is returned to the reference value.

Next, the soft switching operation of the main switch Q1 based on the auxiliary circuit 7 will be described with reference to FIG.

(Before t1) In the period before t1 in FIG. 4, both the main switch Q1 and the auxiliary switch Q2 are off. Therefore, before t1 in FIG. 4, t3 to t in FIG.
The same operation as in period 5 occurs and the current Ido of diode Do
Flows as shown in FIG. 4 (H), and the voltage Vq1 of the main switch Q1 and the voltage Vq2 of the auxiliary switch Q2 are shown in FIG. 4 (C).
It is kept at a high level as shown in (E).

(T1 to t2 period) When the auxiliary switch Q2 is turned on at the time t1 in FIG. 4, the smoothing capacitor C
1, a current Iq2 flows in the path of the tertiary winding N3, the auxiliary diode Da and the auxiliary switch Q2 as shown in FIG. 4 (F). When the above-mentioned current Iq2 flows through the tertiary winding N3, a voltage is generated in the secondary winding N2 in the direction that reversely biases the output rectifying diode Do, so that this diode Do is converted to non-conducting, and the diode Do is converted to the non-conductive state as shown in FIG. ), The current Ido of the diode Do becomes zero. As a result, the state in which the primary winding N1 is clamped at the output voltage Vo via the secondary winding N2 is eliminated. Further, a voltage in the opposite direction to the voltage of the smoothing capacitor C1 is generated in the primary winding N1 based on the current of the tertiary winding N3. As a result, the soft switching capacitor C
q1 can be discharged, and the discharge current of the soft switching capacitor Cq1 flows through the path of the soft switching capacitor Cq1, the primary winding N1, the tertiary winding N3, the auxiliary diode Da and the auxiliary switch Q2, and the main switch Q1. Voltage Vq1 gradually decreases as shown in FIG.
It becomes substantially zero at that point. Since the tertiary winding N3 in series with the auxiliary switch Q2 has an inductance La, the discharge current of the soft switching capacitor Cq1 is a resonance operation between the capacitance of the capacitor Cq1 and the inductance La of the tertiary winding N3. The current Iq2 of the auxiliary switch Q2 gradually increases from t1. Therefore, the auxiliary switch Q2 is switched at zero current at time t1, and the switching loss when the auxiliary switch Q2 is turned on is small.

(T2 to t3 period) When the discharge of the soft switching capacitor Cq1 is completed at time t2, the energy stored in the inductance La of the tertiary winding N3 is discharged, and the result is shown in FIGS. Current Iq1, Iq2
Flows in the path of the tertiary winding N3, the first auxiliary diode Da, the auxiliary switch Q2, the parallel diode Dq1, and the primary winding N1. The current Iq2 flowing through the auxiliary switch Q2 gradually decreases from the time point t2. Also, the first parallel diode Dq
The current of 1 also gradually decreases from the time point t2. Note that FIG.
The current Iq1 in (D) is represented by the sum of the drain-source current of the main switch Q1 and the parallel diode Dq1. Here, the current Iq1 is referred to as the current of the main switch Q1 in order to simplify the description. When the main switch Q1 is turned on at t2 or the first parallel diode Dq1 is turned on, the voltage Vc1 of the smoothing capacitor C1 is applied to the primary winding N1. The stored energy of the inductance La of the tertiary winding N3 is equal to the tertiary winding N3,
It is also discharged through the path consisting of the first auxiliary diode Da, the auxiliary switch Q2, and the smoothing capacitor C1. Current flowing through the parallel diode Dq1, that is, current Iq1 of the main switch Q1
Becomes zero at t3. The parallel diode Dq1 is t in FIG.
Since it is in the ON state during the period from 2 to t3, the voltage Vq1 of the main switch Q1 is maintained at substantially zero during the period from t2 to t3.
Therefore, if the main switch Q1 is turned on during the period from t2 to t3, ZVS of the main switch Q1 is achieved. Figure 4
In (A), the control signal Vg1 of the main switch Q1 changes from low level to high level at time t2. However, considering the variation in the turn-on control of the main switch Q1, t2
It is desirable to start the ON control of the main switch Q1 in the middle of the period t3. However, even if the ON control start time of the main switch Q1 is before t2 when the voltage Vq1 of the main switch Q1 becomes zero, if this voltage Vq1 starts decreasing from the time t1, this voltage Vq1 It is possible to obtain the effect of reducing the switching loss as much as the reduction. Also,
Even if the ON control start time of the main switch Q1 is slightly after t3, the switching loss reducing effect can be obtained. That is, since the main switch Q1 does not turn on at t3, even if charging of the resonance capacitor Cq1 is started, the voltage of this capacitor Cq1 must be within a range lower than the voltage Vq1 of the off period of the main switch Q1 before t1. If this is the case, the switching loss is reduced by the lower amount. Therefore, the time when the ON control of the main switch Q1 can start is the auxiliary switch Q2.
After the time point t1 when the ON control is performed and at a time point during which the voltage Vq1 of the main switch Q1 is lower than the voltage Vq1 of the main switch Q1 in the OFF period shown before t1. Since FIG. 4 shows the state within the period from t1 to t6 of FIG. 3, the parallel diode D at the time of t2 of FIG.
When q1 becomes conductive, the current I flowing through the main inductor L1
_L1 begins to flow as shown in FIG.

(T3 to t4 period) When the parallel diode Dq1 cannot maintain the ON state at the time t3, the current Iq1 of the main switch Q1 becomes zero, and thereafter,
The current Iq1 flows in the positive direction. In this t3 to t4 period,
A first path consisting of a rectifier circuit 4, a main inductor L1, a second part N1b of the primary winding N1, and a main switch Q1;
Smoothing capacitor C1, primary winding N1 and main switch Q
The current Iq1 of the main switch Q1 shown in FIG. 4 (D) flows through both the second path consisting of 1 and 1. In this embodiment, the discharge of the energy stored in the inductance La of the tertiary winding N3 does not end at time t3 but ends at time t4. Therefore, in the period from t3 to t4, the tertiary winding N3
, The first auxiliary diode Da, the auxiliary switch Q2, and the smoothing capacitor C1 through the path Iq2 shown in FIG.
Flows. In the period t3 to t4, as in the period t4 to t5, the voltage of the smoothing capacitor C1 is applied to the primary winding N1 and the diode Do of the rectifying and smoothing circuit 6 is non-conductive. The energy on the secondary side is stored in the transformer 5.

(T4 to t5 period) During the t4 to t5 period,
The current Iq2 of the auxiliary switch Q2 is kept at zero as shown in FIG. 4 (F), and the current Iq1 of the main switch Q1 flows as shown in FIG. 4 (D). During the period from t4 to t5, as in the period from t3 to t4, the first AC input terminal 1, the filter 3, the first
Diode D1, inductor L1, second portion N1b of primary winding N1, main switch Q1, fourth diode D4
A filter, a filter 3 and a second AC input terminal 2
A current for power factor improvement and waveform improvement in the path of (1) and a current for DC-DC conversion in the second path composed of the smoothing capacitor C1, the primary winding N1 and the main switch Q1 flow. First above
The current in the path is equal to the current I _L1 of the inductor L1 shown in FIG. During the period from t4 to t5, 2 shown in FIG.
The current Ido of the next diode Do is kept at zero.
Therefore, nergi is accumulated in the transformer 5 during the period from t4 to t5.

During the period from t4 to t5 in FIG. 4, the primary winding N1
A voltage in the opposite direction to the voltage Vc1 of the smoothing capacitor C1 is induced in the tertiary winding N3 on the basis of the above voltage. As a result, the auxiliary diode Da is kept non-conductive, and
The voltage Vq2 of the auxiliary switch Q2 is maintained at zero as shown in (E), and the auxiliary switch Q2 as shown in FIG.
Current Iq2 of is kept at zero. Therefore, t4 to t5 in FIG.
When the auxiliary switch Q2 is turned off at any time during the period, ZVS and zero current switching or ZCS is achieved. In this embodiment, the end time of the ON control of the auxiliary switch Q2 is the same t5 time as the end time of the ON control of the main switch Q1. Therefore, the ZVS and ZCS conditions of the auxiliary switch Q2 are satisfied, and the switching loss when the auxiliary switch Q2 is turned off is small. As described above, during the period from t4 to t5 in FIG. 4, the ZVS and ZCS of the auxiliary switch Q2 are possible, so that FIG.
The turn-off time of the auxiliary switch Q2 can be moved to t4 as shown by the dotted line in (B), or can be moved to any time between t4 and t5.

(T5 to t6 period) When the main switch Q1 is turned off at time t5, the current Iq1 of the main switch Q1 becomes zero as shown in FIG. 4D, and the soft switching capacitor Cq1 is charged. The main switch Q
The voltage Vq1 of 1 has a slope and gradually increases as shown in FIG. Therefore, the main switch Q1 is turned off at ZVS. The charging current of the soft switching capacitor Cq1 is the smoothing capacitor C1 and the rectifying circuit 4, the inductor L1, the second portion N1b of the primary winding N1, and the first path of the soft switching capacitor Cq1.
It flows through the primary winding N1 and the second path of the soft switching capacitor Cq1.

(T6 to t7 period) In the t6 to t7 period,
By discharging the stored energy of the inductor L1 and the transformer 5, a voltage is generated in the secondary winding N2 so as to forward-bias the diode Do, and this diode Do has a voltage shown in FIG.
The current Ido shown in (H) flows. Further, the charging current of the smoothing capacitor C1 flows through the path of the rectifier circuit 4, the inductor L1, the first portion N1a of the primary winding N1 and the smoothing capacitor C1.

(T7-t8 period) The current I _{L1 of the} inductor L1 becomes zero at t7 as shown in FIG. 4 (G). This t
After time 7, the conduction of the diode Do is maintained by discharging the stored energy of the transformer 5. When the auxiliary switch Q2 is turned on again at the time point t8, the same operation as in the period t1 to t8 is repeated.

According to this embodiment, the following effects can be obtained. (1) Since ZVS is set both when the main switch Q1 is turned on and when it is turned off, the main switch Q1
It is possible to reduce the switching loss of 1 and improve the efficiency of the switching power supply device. (2) Auxiliary switch Q2 is zero current switching (ZCS) at turn-on, and ZVS and Z at turn-off.
CS is done. As a result, the switching loss of the auxiliary switch Q2 can be suppressed low. (3) Since the peak value of the current I _L1 passing through the inductor L1 changes following the amplitude of the AC input voltage Vac, the power factor and waveform of the AC input are improved. This power factor improvement and waveform improvement are performed with the help of the main switch Q1 in the DC-DC converter circuit including the smoothing capacitor C1, the transformer 5, the main switch Q1 and the rectifying / smoothing circuit 6. Therefore, it is possible to achieve power factor improvement, waveform improvement, and output voltage adjustment with a simple circuit. (4) Since the tertiary winding N3 of the auxiliary circuit 7 for reducing the switching loss of the main switch Q1 is formed integrally with the transformer 5 for the DC-DC converter, the switching power supply device is increased in size and cost. The rise can be suppressed. (5) Since the inductor L1 is connected to the tap 10 of the primary winding N1, even if the main switch Q1 is on, the potential of the first rectified output conductor 43 must be higher than the potential of the tap 10. The current I _{L1 of the} inductor L1 does not flow. Therefore, t0 to t1, t6 to t8, t9 to
The current I _{L1 of the} inductor L1 does not flow during the period t10, which is disadvantageous in terms of waveform improvement and power factor improvement. However, there is no power loss here during the period when no current flows through the inductor L1. Therefore, the position of the tap 10 can be adjusted to increase the efficiency within the range where the required waveform improvement and power factor improvement can be achieved.

[0038]

Second Embodiment Next, a switching power supply device according to a second embodiment will be described with reference to FIG. However, in FIG. 6 and FIGS. 7 to 20 to be described later, the same reference numerals are given to the substantially same parts as FIGS. 1 to 5, and the description thereof will be omitted. Also, refer to FIG. 3 and FIG. 4 as necessary.

The switching power supply device of FIG. 6 is different from that of FIG. 1 except that the connection relationship between the main inductor L1 and the primary winding N1 is changed.
The circuit is the same as that of. The transformer 5a shown in FIG. 6 has a primary winding N1, a secondary winding N2, and a tertiary winding N3 that do not have taps.
It consists of and. The main inductor L1 in FIG. 6 is connected to the interconnection point between the primary winding N1 and the main switch Q1. Therefore, the main inductor L1 is connected to the smoothing capacitor C1 via the entire primary winding N1, and is connected to the main switch Q1 without the primary winding N1 at all.

In the switching power supply device of FIG. 6, when the main switch Q1 is turned on, t0 to t1 and t6 of FIG.
.About.t8, t9 to t10, the first rectified output conductor 43, the main inductor L1, the main switch Q1, and the second rectified output conductor 4 are also used in a region where the amplitude of the AC input voltage Vac is low.
The current I _L1 flows through the route of 5. As a result, the switching power supply device of FIG. 6 is characterized in that the effect of improving the waveform and the power factor is greater than that of the switching power supply device of FIG. However, since the current I _L1 flows through the main inductor L1 in almost all of one cycle of the AC power supply voltage Vac, the power loss here becomes large, and the efficiency of the switching power supply device is lower than that of the switching power supply device of FIG. To do. Therefore, when high efficiency is required, the switching power supply device of FIG. 1 is used, and when it is desired to improve waveform improvement and power factor improvement of the switching power supply device of FIG. 1, the switching power supply device of FIG. 6 is used. Since the switching power supply device of FIG. 6 has the same soft switching auxiliary circuit 7 as in FIG. 1, the effect of reducing the switching loss by this auxiliary circuit 7 can be obtained similarly to the circuit of FIG.

[0041]

Third Embodiment A switching power supply device according to a third embodiment shown in FIG. 7 has the same configuration as that of FIG. 1 except that the connection position of the auxiliary circuit 7 in the circuit of FIG. 1 is changed. The series circuit consisting of the tertiary winding N3, the auxiliary diode Da and the auxiliary switch Q2 in the auxiliary circuit 7 of FIG. 7 is the primary winding.
It is connected in parallel to the main switch Q1 without N1.
The series circuit is connected in parallel to the smoothing capacitor C1 via the primary winding N1.

The operation of the main circuit portion except the auxiliary circuit 7 of FIG. 7 is the same as the operation of the main circuit portion of FIG. Also, FIG.
The operation of the auxiliary circuit 7 is essentially the same as that of the auxiliary circuit 7 of FIG. Therefore, the waveform of each part of FIG. 7 is substantially the same as that of FIG. 4 showing the waveform of each part of FIG. Therefore, the operation of the circuit of FIG. 7 will be described with reference to FIG.

At time t1 in FIG. 4, the auxiliary switch Q2 in FIG.
Is turned on, a current Iq2 flows through the path of the smoothing capacitor C1, the primary winding N1, the auxiliary winding N3, the auxiliary diode Da and the auxiliary switch Q2. When a current starts to flow in the auxiliary winding N3 from the time t1, the secondary winding N2 of the transformer 5
A voltage in the direction for reverse biasing the diode Do is generated in the diode Do, and the diode Do becomes non-conductive as shown in FIG. As a result, the clamping of the primary winding N1 via the secondary winding N2 by the voltage Vo of the capacitor Co is released,
The soft switching capacitor Cq1 starts to discharge,
The discharge current of the soft switching capacitor Cq1 flows through the path of the soft switching capacitor Cq1, the tertiary winding N3, the auxiliary diode Da and the auxiliary switch Q1. As a result, as shown in FIG. 4C, the voltage Vq1 of the main switch Q1 is
Gradually decreases from the time t1 and becomes almost zero at the time t2. Therefore, when the main switch Q1 is turned on at the time t2 or the time t2 to t3, the ZVS of the main switch Q1 is achieved. Since the auxiliary winding N3 has an inductance La,
The current Iq1 flowing through the auxiliary switch Q2 during the period from t1 to t2 gradually increases as shown in FIG.

When the discharge of the soft switching capacitor Cq1 ends at time t2 in FIG. 4 and the main switch Q1 is turned on at time t2 as shown in FIG.
The first winding consisting of the tertiary winding N3, the auxiliary diode Da, the auxiliary switch Q2 and the first parallel diode Dq1 due to the release of the energy stored in the tertiary winding N3 during the period from to t2.
Current flows through the third path N3, the auxiliary winding Da, the auxiliary switch Q2, the smoothing capacitor C1 and the second winding N1. The current Iq2 of the auxiliary switch Q2 in the auxiliary circuit 7 gradually decreases from the time t2 and becomes zero at the time t4 as shown in FIG. 4 (F). Therefore, when the auxiliary switch Q2 is turned off in the period of t4 to t5, ZVS is achieved.

When the main switch Q1 is turned off at the time t5, the soft switching capacitor Cq1 is gradually charged and ZVS is achieved as in the case of FIG.

Auxiliary circuit 7 of the switching power supply device of FIG.
And the inductance L1 work similarly to the auxiliary circuit 7 and the inductance L1 in FIG. 1, the switching power supply device of the third embodiment has the same effect as the switching power supply device of the first embodiment.

[0047]

[Fourth Embodiment] A switching power supply device according to a fourth embodiment shown in FIG. 8 has a main inductor L1 of the switching power supply device according to the third embodiment shown in FIG. It is connected to the interconnection point with the main switch Q1 and is otherwise formed in the same manner as in FIG. Therefore, the modified transformer 5a of FIG. 8 has a primary winding N without taps.
1 and a secondary winding N2 and a tertiary winding N3 as an auxiliary winding.

In the switching power supply device of FIG. 8, the operation of the main circuit including the main inductor L1 and the main switch Q1 is as shown in FIG.
And has the same effect as the circuit of FIG.
Since the auxiliary circuit 7 is formed and connected in the same manner as that of FIG. 7, the main switch Q1 is the same as that of FIG.
ZVS or soft switching can be achieved.

[0049]

[Fifth Embodiment] A switching power supply device according to a fifth embodiment shown in FIG. 9 is obtained by adding an auxiliary charging circuit 30 and a reverse current element diode D5 as a second auxiliary circuit to the circuit of FIG. Is formed in the same manner as in FIG. The auxiliary charging circuit 30 can also be called a charge adding circuit, and includes the auxiliary charging winding N4 and the auxiliary charging capacitor C.
2, first and second auxiliary charging diodes D6, D7,
And an auxiliary inductor L2 for charging. The auxiliary charging circuit 30 is connected between the auxiliary rectifying output conductor 44 and the smoothing capacitor C1 and generates a rectified output voltage V4 obtained between the auxiliary rectifying output conductor 44 and the second rectifying output conductor 45. Form an auxiliary voltage for addition.

One end (lower end) of the auxiliary charging winding N4 is connected to one end (upper end) of the primary winding N1 and one end (upper end) of the smoothing capacitor C1. The other end (upper end) of the auxiliary charging winding N4 is an auxiliary charging capacitor C2, an auxiliary charging inductor L2 and a second auxiliary charging diode D.
7 to the auxiliary rectification output conductor 44.
The first charging auxiliary diode D6 is connected in parallel to the charging auxiliary winding N4 via the charging auxiliary capacitor C2. The auxiliary charging capacitor C2 is connected between the other end of the auxiliary charging inductor L2 and the other end of the auxiliary charging winding N4. The anode of the first auxiliary charging diode D6 is connected to the interconnection point between the auxiliary charging capacitor C2 and the auxiliary charging inductor L2. Auxiliary charging circuit 3
An auxiliary rectified output conductor 44 for connecting 0 is connected to the interconnection point 48 of the first and third diodes D1 and D3.

The transformer 5b in FIG. 9 is the transformer 5 in FIG.
A charging auxiliary winding N4 consisting of a quaternary winding is added to the above, and the other components are the same as the transformer 5 shown in FIG. The auxiliary charging winding N4 is electromagnetically coupled to the primary winding N1 and the secondary winding N2. The backflow prevention diode D5 is connected in series with the main inductor L1.

The operation of the switching power supply device of FIG. 9 excluding the auxiliary charging circuit 30 is substantially the same as the operation of the switching power supply device of FIG. In the circuit of FIG. 9, the first and second AC input terminals 1 and 2 are connected to an AC power source, and the switch Q1 makes one cycle of the ON period Ton of t2 to t3 and the OFF period Toff of t3 to t4 in FIG. When T is repeatedly turned on and off, the smoothing capacitor C
1 is charged to a desired DC voltage Vc1. Further, the auxiliary charging capacitor C2 is charged to the voltage Vc2 by the voltage of the auxiliary charging winding N4. The voltage of the smoothing capacitor C1 is V
The charging auxiliary capacitor C2 is charged to c1 and the voltage Vc2
The operation of the main circuit portion of the switching power supply device and the auxiliary charging circuit 30 in the normally charged state will be described below with reference to FIG. FIG. 10 schematically shows the state of each part of FIG. 9 similarly to FIG. A control signal having a repetition frequency of, for example, 20 kHz schematically shown in FIG. 10A in a state where an AC voltage Vac of, for example, 50 Hz shown in FIG. 10E is supplied between a pair of AC input terminals 1 and 2. When the switch Q1 is turned on / off by Vg1, the amplitude of the current Iq1 of the main switch Q1 shown in FIG. 10 (C) and the amplitude of the output current I4 of the rectifier circuit 4 shown in FIG. 10 (B) depend on the amplitude of the AC voltage Vac. Change. As a result, the AC input current Iac shown in FIG. 10D approximates to a sine wave, and the power factor and the waveform are improved. The current I4 in FIG. 10B is shown as a current flowing through the interconnection point 48 of the first and third diodes D1 and D3 in FIG. Therefore, the rectified output current I4
Is the current I _L2 of the main inductor L1 and the auxiliary inductor _L2.
And has the value of the sum of. Since the main inductor L1 is connected to the tap 10 of the primary winding N1 via the backflow prevention diode D5, it is given by the voltage Vc1 of the smoothing capacitor C1 even if the main switch Q1 is in the ON state. During the periods t0 to t1, t6 to t8 and t9 to t10 when the voltage of the tap 10 becomes higher than the rectified output voltage V4,
Current I _L1 and AC input current Iac of the main inductor L1 does not flow. In FIG. 10, the rectified output current I4 and the AC input current Iac flow during the periods t1 to t6 and t8 to t9.

The circuit of FIG. 9 is roughly divided into first and second circuits according to the change in the instantaneous value of the AC power supply voltage Vac shown in FIG. 10 (E).
And in the third mode. Now, taking the section of the AC power supply voltage Vac from 0 to 180 degrees as an example, the AC power supply voltage Vac takes a value between 0V and the first voltage value Va, t0.
During the period from t1 to t6 and t6 to t7, the first mode is set, and the AC power supply voltage Vac takes a value between the first voltage Va and the second voltage Vb, and during the second period during t1 to t3 and t5 to t6. The mode is entered, and the third mode is entered during the period t3 to t5 when the AC power supply voltage Vac becomes higher than the second value Vb. Here, the first voltage value Va represents the voltage between the tap 10 of the primary winding N1 and the ground conductor 45 during the ON period of the main switch Q1, and the second voltage value Vb is the smoothing capacitor C.
A voltage Vc1 of 1 is shown. In addition, the AC power supply voltage Vac
It is shown that the time point at which the value Vb of the voltage Vb crosses coincides with the time point at which the ON period Ton of the main switch Q1 ends. Further, the negative half-wave of t7 to t10 of the AC power supply voltage Vac of FIG. 10 (E) is rectified by the rectifier circuit 4 and becomes a positive half-wave of t0 to t7 in the state of the rectified output voltage V4 after rectification. Be the same. Therefore, even in the negative half-wave period from t7 to t10, t0
The first to third modes occur similarly to the positive half-wave period of t7.

First, in FIG. 10, t0 to t1 and t6 to t7
The operation in the first mode period will be described. This first mode
During the period, when the switch Q1 is turned on, the smoothing coil
Path of capacitor C1, primary winding N1 and main switch Q1
Then, the current Iq1 of the main switch Q1 shown in FIG.
It At this time, the diode Do on the secondary side was kept in the off state.
Energy is released to the secondary side via the transformer 5b.
Energy is not stored, and energy is stored in the transformer 5b. this
During the first mode period, the tap 10 of the primary winding N1 is charged.
Since the position is higher than the potential of the first rectified output conductor 43,
Current I through inductor L1_L1Does not flow. Also, the first
During the mode period, the voltage Vc1 of the smoothing capacitor C1 is
Since it is higher than rectified output voltage V4, auxiliary inductor L2
Current I _L2Does not flow. Main switch Q1 turns off
And the secondary winding due to the release of the stored energy of the transformer 5c.
The circuit of line N2, diode Do and capacitor Co is charged.
The flow flows. Therefore, the instantaneous value of the AC power supply voltage Vac is low.
Even during the period, power is supplied to the capacitor Co and the load 13.
Can be supplied.

In FIG. 10E, t1 to t3 and t5 to t6.
During the second mode period, the potential of the tap 10 of the primary winding N1 becomes lower than the potential of the first rectified output conductor 43, so that the current I _L1 flows through the main inductor L1. When the main switch Q1 is turned on in the second mode period, the first rectified output conductor 43, the main inductor L1, the reverse current blocking diode D5, and the second portion N1 of the primary winding N1.
b, the current I _L1 flows through the first path composed of the main switch Q1 and the common rectified output conductor 45, and at the same time, the current flows through the second path composed of the smoothing capacitor C1, the primary winding N1 and the main switch Q1. Flowing. Therefore, the current Iq1 of the main switch Q1 shown in FIG. 10C is the sum of the currents of the first and second paths. During the second mode period, the voltage Vc1 of the smoothing capacitor C1 is higher than the rectified output voltage V4, so that the diode D7 is kept off. The off period Tof of the main switch Q1 shown at t3 to t4 in FIG.
A current I _L1 that charges the smoothing capacitor C1 with the release of the stored energy of the main inductor L1 flows through f, and the diode is released based on the release of the stored energy of the transformer 5b and the main inductor L1 to the secondary side. Do is conducting,
This current Ido flows. The current I _L1 of the main inductor L1 decreases as the stored energy of the transformer 5b and the main inductor L1 progresses.

Since the AC input voltage Vac and the rectified output voltage V4 thereof are higher than the voltage Vc1 of the smoothing capacitor C1 during the third mode period shown by t3 to t5 in FIG.
And the second auxiliary charging diodes D6 and D7 are turned on. As a result, it flows both the current I _L1 of the main inductor L1 and a current I _L2 of the auxiliary inductor L2. The operation in the third mode period will be described with reference to FIG. The first control signal Vg of FIG. 11A is obtained from to to t1 of FIG.
When the main switch Q1 is turned on in response to 1, the current I _L1 of the main inductor L1 shown in FIG. 11 (F) flows along the same path as in the second mode period described above, and the smoothing capacitor C1 and the primary capacitor A current also flows through the circuit of the winding N1 and the main switch Q1. The current Iq1 of the main switch Q1 shown in FIG. 11 (E) is the sum of the current IL1 of the main inductor _L1 and the discharge current (not shown) of the smoothing capacitor C1 shown in FIG. 11 (F).

During the on period Ton of the main switch Q1, the voltage Vn4 determined by the turn ratio between the primary winding N1 and the auxiliary charging winding N4 is shown in the auxiliary charging winding N4 as shown in FIG. Is obtained as Since the direction of this voltage Vn4 is the direction in which the first auxiliary charging diode D6 is forward biased,
Auxiliary winding N4 for charging, auxiliary capacitor C2 for charging and first
Current flows through the closed circuit of the auxiliary charging diode D6 of, and the auxiliary charging capacitor C2 is charged to the polarity shown in FIG.
The voltage of the auxiliary charging capacitor C2 becomes Vc2. In the auxiliary inductor L2, the current I _L2 similar to that in the period t1 to t2 has already flowed in the off period before the on period from t0 to t1 in FIG. The potential on the anode side of the first charging auxiliary diode D6 during the on period Ton of the main switch Q1, that is, on the right end side of the auxiliary inductor L2 is on the anode side of the first charging auxiliary diode D6 during the off period Toff of the main switch Q1. Since it becomes higher than the potential, the current I _L2 of the auxiliary inductor L2 gradually decreases as shown in FIG. The path of the current I _L2 flowing through the auxiliary inductor L2 during the ON period Ton is as follows: the first AC input terminal 1, the filter 3, the first diode D1, the second charging auxiliary diode D7, the auxiliary inductor L2, and the first inductor D2. Auxiliary diode D6 for charging, smoothing capacitor C1, fourth diode D
4, a path formed by the filter 3, and the second AC input terminal 2. The current I _L2 of the auxiliary inductor L2 increases as the instantaneous value of the AC input voltage Vac increases.

As shown at t1 to t2 in FIG.
When the switch Q1 turns off, the current I in the main inductor L1_L1To
The charging of the smoothing capacitor C1 by the above-mentioned second mode
The same as during the period, and as shown in FIG.
The current Ido is supplied to the diode Do as a secondary side rectifier.
Flowing. In addition, the secondary winding N2 is the voltage V of the capacitor Co.
Figure 1 shows the auxiliary winding N4 for charging to be clamped at o.
The voltage Vn4 shown in 1 (H) is obtained. Off period Toff
The direction of the voltage Vn4 of the auxiliary charging winding N4 depends on the on period Ton.
Is the opposite of the direction of the first auxiliary diode D6 for charging.
It is in the direction of reverse bias. Of this off period Toff
The voltage Vn4 of the auxiliary winding N4 for charging is the smoothing capacitor C
Since the voltage is in the opposite direction of the voltage Vc1 of 1, the auxiliary inductor
The potential of the right terminal of L2 is lower than that during the ON period.
The current I of the auxiliary inductor L2 _L2During the off period Toff
Gradually increase. The current flowing through this auxiliary inductor L2
Flow I_L2Is the first AC input terminal 1, the filter 3, the first
Diode D1, second charging auxiliary diode D7, auxiliary
Auxiliary inductor L2, auxiliary capacitor C2 for charging, charging
Auxiliary winding N4, smoothing capacitor C1, fourth diode
In the path of D4, filter 3 and second AC input terminal 2
It is used to charge the smoothing capacitor C1. Third
Of the current I through the main inductor L1 during the mode period of_L1When
Current I by auxiliary inductor L2_L2And for both smoothing
The capacitor C1 is charged. Therefore, the smoothing capacitor
The voltage Vc1 of C1 is the voltage of the main inductor L1 of the circuit of FIG.
Flow I_L1It will be higher than when charging only.

The current I4 passing through the rectifier circuit 4 of FIG.
Is the sum of the currents I _L1 and I _L2 of the main and auxiliary inductors L1 and L2 shown in FIGS. Note that the waveforms in FIG. 11 show changes with time, and their amplitudes are not shown faithfully.

According to the embodiment of FIG. 9, the main inductor L
Based on 1 and the auxiliary circuit 7, the same effect as that of the first embodiment can be obtained, and further, the following effect can be obtained based on the auxiliary charging circuit 30. (1) The smoothing capacitor C1 is composed of a rectifier circuit 4, a main inductor L1, a reverse current blocking diode D5 and a primary winding N1.
Is charged by the auxiliary charging circuit 30 as well as by the main charging circuit comprising the first portion N1a of Therefore, assuming that the smoothing capacitor C1 is charged to the same voltage value in the circuit of FIG. 1, the current I _L1 flowing in the main inductor L1 in the circuit of FIG. 9 is higher than that of the circuit of FIG.
Can be made smaller, the main inductor L1 can be made smaller, and the power loss can be reduced here, so that the efficiency of the switching power supply device can be increased. That is, the current I _L1 of the main inductor L1 can be set small within the range where the required input current waveform improvement and power factor improvement can be achieved, and the power loss here can be reduced. The auxiliary charging circuit 30 also has power loss,
Since only the charging current of the smoothing capacitor C1 flows through the auxiliary charging circuit 30, and a large current does not flow, the power loss of the auxiliary charging circuit 30 does not increase so much. Therefore, the circuit of FIG. 9 is superior to the conventional circuit in terms of efficiency and miniaturization. (2) In the circuit of FIG. 9, if the main inductor L1
Assuming that the current for charging the smoothing capacitor C1 flowing through is set to the same as in the circuit of FIG.
The voltage Vc1 of the smoothing capacitor C1 of the
It is higher than that of the circuit of FIG. 1 by the amount of charging by zero. When the voltage Vc1 of the smoothing capacitor C1 becomes high, the peak value of the rectified output voltage V4 or the peak of the current flowing into the smoothing capacitor C1 in the vicinity thereof can be suppressed, and the harmonic component of the input current is reduced. (3) The second auxiliary charging diode D7 blocks the reverse flow of current from the auxiliary charging circuit 30 side to the main inductor L1 side. Thus is reduced the current I _L1 of the main inductor L1, the power loss in this case is reduced.

[0061]

[Sixth Embodiment] A switching power supply device according to a sixth embodiment shown in FIG. 12 includes a main inductor L1 and a primary winding N1.
The configuration is the same as that shown in FIG. 9 except that the connection relationship with is changed. That is, in the circuit of FIG. 12, the main inductor L1 is connected to the interconnection point between the primary winding N1 and the main switch Q1 via the backflow blocking diode D5. The transformer 5c of FIG. 12 corresponds to the transformer 5b of FIG. 9 from which the tap 10 is omitted from the primary winding N1. Since the relationship between the main inductor L1 and the primary winding N1 in the circuit of FIG. 12 is the same as those in the circuit of FIG. 6, the sixth embodiment of FIG. 12 corresponds to the fifth embodiment of FIG. The effect of form and FIG.
And the effect of the second embodiment.

[0062]

[Seventh Embodiment] A switching power supply device according to a seventh embodiment shown in FIG. 13 has the same configuration as that of FIG. 9 except that the auxiliary charging circuit 30 in the circuit of FIG. 9 is modified into an auxiliary charging circuit 30a. It is a thing. Auxiliary charging circuit 30a of FIG.
Then, the first charging auxiliary diode D6 is connected between the auxiliary inductor L2 and the auxiliary charging winding N4, and the auxiliary charging capacitor C2 is connected between the auxiliary inductor L2 and the smoothing capacitor C1. . The auxiliary charging circuit 30a shown in FIG. 13 is different from the auxiliary charging circuit 30a shown in FIG.
The auxiliary charging circuit 30 is formed in the same manner.

The operation of the part other than the auxiliary charging circuit 30a of the switching power supply device of FIG. 13 is substantially the same as that of the switching power supply device of FIG. Therefore, the description of the operation relating to the power factor improvement and the waveform improvement in the circuit of FIG. 13 is omitted.

In the switching power supply device of FIG.
The voltage generated in the auxiliary charging winding N4 during the ON period of the main switch Q1 has a direction for reverse biasing the first auxiliary auxiliary diode D6. Therefore, during the ON period of the main switch Q1, the current for charging the auxiliary charging capacitor C2 is the first
The auxiliary diode D6 for charging does not flow. Main switch Q
During the OFF period of 1, a voltage in the direction for forward biasing the first charging auxiliary diode D6 is obtained in the charging auxiliary winding N4, so that the charging auxiliary winding N4, the charging auxiliary capacitor C2, and the A closed circuit is formed with the auxiliary charging diode D6, and the charging current of the auxiliary charging capacitor C2 flows.

Now, ignoring the voltage drop of the second auxiliary charging diode D7, the voltage between the input side terminal of the auxiliary inductor L2 and the second rectified output conductor 45 coincides with the rectified output voltage V4, Output terminal of inductor L2 and second
The voltage between the rectified output conductor 45 and the smoothing capacitor C
It corresponds to a value Vc1-Vc2 obtained by subtracting the voltage Vc2 of the auxiliary capacitor C2 from the voltage Vc1 of 1. Therefore, the voltage V _L2 of the auxiliary inductor _{L2, V L2 = V4 - (Vc1} -Vc2) = V
It becomes 4-Vc1 + Vc2. Auxiliary inductor L2 current I _L2
Flows based on V4 -Vc1 + Vc2, the current I _L2 flows only when V4 + Vc2 is higher than Vc1. The smoothing capacitor C1 is charged by both the current I _L1 passing through the main inductor L1 and the current I _L2 passing through the auxiliary inductor L2 as in the fifth embodiment of FIG. 9, and the voltage Vc1 of the smoothing capacitor C1 is shown in FIG. The circuit will be higher than this. Therefore, FIG.
The same effect as that of the fifth embodiment of FIG. 9 can be obtained also by the third embodiment of the third aspect.

[0066]

[Eighth Embodiment] A switching power supply device of an eighth embodiment shown in FIG. 14 shows a connection relation between a main inductor L1 and a primary winding N1 of the seventh embodiment shown in FIG.
The embodiment is modified in the same manner as in the above embodiment, and the other parts are formed in the same manner as in FIG. That is, in the eighth embodiment of FIG. 14, the main inductor L1 is the reverse current blocking diode D5.
Is connected to the interconnection point between the primary winding N1 and the main switch Q1. Therefore, the eighth embodiment of FIG. 14 has the same effect as the sixth embodiment of FIG. 12 and the seventh embodiment of FIG.

[0067]

[Ninth Embodiment] A switching power supply device according to a ninth embodiment shown in FIG. 15 has the same circuit as that of the third embodiment shown in FIG. The same element as the diode D5 is added, and the other elements are formed in the same manner as in FIG. The auxiliary charging circuit 30 of FIG. 15 is formed in the same manner as the auxiliary charging circuit 30 of FIG. 9, and operates in the same manner. Therefore, the ninth embodiment of FIG. 15 corresponds to the third embodiment of FIG.
It has both the effects of the above embodiment and the effects of the fifth embodiment of FIG.

[0068]

[Tenth Embodiment] A switching power supply device according to a tenth embodiment shown in FIG. 16 is the same as the circuit shown in FIG. 15 except that the main inductor L1 of the ninth switching power supply device shown in FIG. It was formed in. In FIG. 16, the main inductor L1 is connected to the primary winding N via the backflow blocking diode D5 as in the sixth embodiment of FIG.
It is connected to the interconnection point between 1 and the main switch Q1.
The transformer 5c of FIG. 16 is formed similarly to the transformer 5c of FIG.

In the circuit of the tenth embodiment of FIG. 16, the main circuit and the auxiliary circuit 7 are the same as those of the fourth embodiment of FIG. 8, and the auxiliary charging circuit 30 is the same as the fifth embodiment of FIG. Therefore, it has both the effect of the fourth embodiment and the effect of the fifth embodiment.

[0070]

Eleventh Embodiment A switching power supply device according to the eleventh embodiment shown in FIG. 17 is obtained by modifying the auxiliary charging circuit 30 of the ninth embodiment shown in FIG. 15 into an auxiliary charging circuit 30a. They are formed the same. The auxiliary charging circuit 30a of FIG. 17 is formed and operates in the same manner as the auxiliary charging circuit 30a of the seventh embodiment of FIG. Therefore,
The eleventh embodiment of FIG. 17 has both the effect of the ninth embodiment of FIG. 15 and the effect of the seventh embodiment of FIG.

[0071]

[Twelfth Embodiment] A switching power supply device according to a twelfth embodiment of FIG. 18 is the same as that of FIG. 18 except that the connection portion of the main inductor L1 of the embodiment of FIG. 17 is modified. . The main inductor L1 in FIG. 18 is connected to the interconnection point between the primary winding N1 and the main switch Q1 via the reverse current blocking diode D5 as in the circuit of FIG. Therefore, the primary winding N1 of the transformer 5c in FIG. 18 has no tap.

The twelfth embodiment of FIG. 18 is the fourth embodiment of FIG.
Since the main circuit and the auxiliary circuit 7 are the same as those of the seventh embodiment and the auxiliary charging circuit 30a is the same as that of the seventh embodiment of FIG. 13, the effects of the fourth embodiment and the effects of the seventh embodiment. Having both an effect.

[0073]

[Thirteenth Embodiment] A switching power supply device according to a thirteenth embodiment shown in FIG. 19 corresponds to the seventh embodiment.
An auxiliary charging circuit 30b, which is a modification of the auxiliary charging circuit 30a, is provided, and the other parts are formed in the same manner as in FIG. The auxiliary charging circuit 30b of FIG. 19 corresponds to the auxiliary charging circuit 3 of FIG.
0a to auxiliary capacitor C2 for charging and auxiliary inductor L
2 and the first auxiliary charging diode D6 are omitted. Therefore, the auxiliary charging circuit 30b shown in FIG. 19 includes the auxiliary charging winding N4 and the auxiliary charging diode D7. The auxiliary charging winding N4 is connected between the auxiliary rectifying output conductor 44 and the smoothing capacitor C1 via the auxiliary diode D7 and has a leakage inductance. The auxiliary charging winding N4 has a voltage Vn in the direction for forward biasing the auxiliary charging diode D7 during the off period of the main switch Q1.
4 occurs. The current of the auxiliary charging diode D7 flows only when the sum V4 + Vn4 of the rectified output voltage V4 and the voltage Vn4 of the auxiliary charging winding N4 becomes higher than the voltage Vc1 of the smoothing capacitor C1, which is the smoothing capacitor C1. Used to charge.

The thirteenth embodiment of FIG. 19 is the same as the seventh embodiment of FIG. 13 except that the smoothing effect by the auxiliary inductor L2 and the auxiliary capacitor C2 of the auxiliary charging circuit 30a of FIG. 13 cannot be obtained. The same effect can be obtained, and according to the thirteenth embodiment of FIG. 19, the configuration of the auxiliary charging circuit 30b can be simplified and downsized.

In FIG. 19, the cathode of the reverse current blocking diode D5 is set to 1 as in the circuits of FIGS.
Instead of connecting to the tap 10 of the secondary winding N1, it can be connected to the interconnection point of the primary winding N1 and the main switch Q1.
Further, the auxiliary circuit 7 of FIG. 19 can be connected in parallel to the main switch Q1 as in the third embodiment shown in FIG. In short, FIG. 9, FIG. 12, FIG. 13, FIG.
5, the auxiliary charging circuit 30 or 30a in FIGS. 16, 17 and 18 can be replaced with the auxiliary charging circuit 30b in FIG.

[0076]

[Fourteenth Embodiment] A switching power supply device according to a fourteenth embodiment shown in FIG. 20 is provided with a modified rectifier circuit 4a and a modified auxiliary charging circuit 30c. It is formed in the same way as.

The rectifier circuit 4a of FIG. 20 has fifth to sixth diodes D11 and D12 in addition to the first to fourth diodes D1 to D4 similarly to the rectifier circuit 4 of FIG. The anode of the fifth diode D11 is the first AC input conductor 4
1 and its cathode is connected to the auxiliary rectifying output conductor 44. The anode of the sixth diode D12 is connected to the second AC input conductor 42, and the cathode thereof is connected to the auxiliary rectification output conductor 44. Therefore, the auxiliary rectification output conductor 44 has the first and third diodes D1 and D1.
The rectified output of 3 is not supplied, but the rectified outputs of the fifth and sixth diodes D11 and D12 are supplied instead. The electrical characteristics of the fifth and sixth diodes D11, D12 are substantially the same as the electrical characteristics of the first and third diodes D1, D3. Therefore, the voltage between the auxiliary rectified output conductor 44 and the second rectified output conductor 45 is
And the voltage V4 between the second rectified output conductor 45 is substantially the same.

The auxiliary charging circuit 30c corresponds to the auxiliary charging circuit 30 shown in FIG. 9 with the second auxiliary charging diode D7 omitted. Since the fifth and sixth diodes D11, D12 of the rectifier circuit 4a have a backflow prevention function, even if the second auxiliary charging diode D7 is omitted, the auxiliary charging circuit 30c
Operates similarly to the auxiliary charging circuit 30 of FIG. The fifth and sixth diodes D11 and D12 shown in FIG. 20 are high frequency diodes capable of responding to the change in the current of the auxiliary inductor L2 due to the ON / OFF of the main switch Q1. If the fifth and sixth diodes D11, D12 are low frequency diodes, it is desirable to add the second auxiliary charging diode D7 to the auxiliary charging circuit 30c as in FIG.

The rectifying circuit 4a and the auxiliary charging circuit 3 shown in FIG.
0c operates substantially the same as the rectifier circuit 4 and the auxiliary charging circuit 30 of FIG. 9, the switching power supply device of the thirteenth embodiment has the same effect as the fifth embodiment of FIG. Note that FIG. 12, FIG. 13, FIG. 14, FIG.
Instead of the rectifier circuit 4 of FIGS. 17, 18 and 19, FIG.
The rectifier circuit 4a of can be used.

[0080]

[Modification] The present invention is not limited to the above-described embodiment, and the following modifications are possible. (1) FIG. 9, FIG. 12, FIG. 13, FIG. 14, FIG.
6, the second auxiliary charging diode D7 of the embodiment of FIGS. 17 and 18 can be omitted. When the second auxiliary charging diode D7 is omitted, the period t0 to t1, the period t6 to t8, and the period t9 to t10 shown in FIG.
AC input current Iac of (2) In each embodiment, the first rectified output conductor 43
A bypass capacitor can be connected between the second rectified output conductor 45 and the second rectified output conductor 45. The bypass capacitor is a high frequency capacitor having a capacity sufficiently smaller than that of the smoothing capacitor C1. Thus, for example, in the circuit of FIG. 1, the main inductor L1 is turned off during the off period of the main switch Q1.
The current flowing in the path between the reverse current blocking diode D5, the first portion N1a of the primary winding N1, the smoothing capacitor C1 and the rectifying circuit 4 can be passed through the bypass capacitor without passing through the rectifying circuit 4. . As a result, the noise generated in the diodes D1 to D4 of the rectifier circuit 4 can be reduced. (3) Instead of providing the secondary winding N2 on the transformers 5 to 5c, a known single-winding transformer configuration can be used. Also,
A rectifying / smoothing circuit can be connected to the interconnection point between the primary winding N1 and the main switch Q1 to form a step-up switching power supply device. (4) The reverse current blocking diode D5 can be moved between the first rectified output conductor 43 and the main inductor L1.
Further, when the backflow is not a problem, the backflow blocking diode D5 can be omitted. (5) Main switch Q1 is a transistor other than FET,
A semiconductor switch such as an IGBT (insulated gate bipolar transistor) can be used. (6) The present invention can also be applied to a forward type switching power supply device in which the diode Do on the secondary side conducts during the ON period of the main switch Q1. (7) FIG. 1, FIG. 6, FIG. 9, FIG. 12, FIG.
19 and 20, one end of the auxiliary circuit 7, that is, the upper end of the tertiary winding N3 can be connected to an arbitrary tap 10a of the primary winding N1 as shown by a dotted line.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a switching power supply device of a first embodiment according to the present invention.

FIG. 2 is a block diagram showing the control circuit of FIG. 1 in detail.

FIG. 3 is a waveform diagram schematically showing voltage and current in each part of FIG.

FIG. 4 is a waveform diagram schematically showing voltages and voltages of respective parts in FIG.

5 is a waveform diagram showing a state of each part of FIG.

FIG. 6 is a circuit diagram showing a switching power supply device according to a second embodiment.

FIG. 7 is a circuit diagram showing a switching power supply device according to a third embodiment.

FIG. 8 is a circuit diagram showing a switching power supply device according to a fourth embodiment.

FIG. 9 is a circuit diagram showing a switching power supply device according to a fifth embodiment.

10 is a waveform chart showing a state of each part of FIG.

FIG. 11 is a waveform diagram showing a state of each part of FIG.

FIG. 12 is a circuit diagram showing a switching power supply device according to a sixth embodiment.

FIG. 13 is a circuit diagram showing a switching power supply device of a seventh embodiment.

FIG. 14 is a circuit diagram showing a switching power supply device of an eighth embodiment.

FIG. 15 is a circuit diagram showing a switching power supply device of a ninth embodiment.

FIG. 16 is a circuit diagram showing a switching power supply device of a tenth embodiment.

FIG. 17 is a circuit diagram showing a switching power supply device of an eleventh embodiment.

FIG. 18 is a circuit diagram showing a switching power supply device of a twelfth embodiment.

FIG. 19 is a circuit diagram showing a switching power supply device of a thirteenth embodiment.

FIG. 20 is a circuit diagram showing a switching power supply device of a fourteenth embodiment.

[Explanation of symbols]

5-5c Transformer 7 Auxiliary circuit 30, 30a, 30b, 30c Auxiliary charging circuit N1, N2, N3, N4 Primary, secondary, tertiary and quaternary winding Q1 Main switch C1 Smoothing capacitors L1, L2 Main and auxiliary Inductor C2 Auxiliary capacitor Da, D6, D7 Auxiliary diode

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5H006 AA02 CA02 CA07 CB01 CB08                       DA04 DB01                 5H730 AA18 AS01 BB35 BB43 BB44                       BB57 CC04 DD04 DD34 EE02                       EE07 EE59 FD01 FG05

Claims (13)

[Claims] 1. A switching power supply device for converting an AC voltage supplied from an AC power supply into a DC voltage, comprising first and second AC input terminals (1, 2) for supplying the AC voltage. A rectifying circuit (4 or 4a) connected to the first and second AC input terminals (1, 2) and having first and second rectifying output conductors (43, 45); A transformer (5 or 5a or 5b or 5c) having a wire (N1) and an auxiliary winding (N3) electromagnetically coupled to the main winding (N1), and one end of the main winding (N1) and the first winding (N1). Smoothing capacitor (C1) connected between the two rectified output conductors (45)
And a main inductor having one end connected to the first rectified output conductor (43) and the other end connected to the smoothing capacitor (C1) through at least a part of the main winding (N1). (L1), a main switch (Q1) connected between the other end of the main winding (N1) and the second rectified output conductor (45), and connected in parallel to the main switch (Q1). A capacitance means (Cq1) for soft switching consisting of a charged capacitor or a parasitic capacitance, a rectifying / smoothing circuit (6) connected to the transformer (5 or 5a or 5b or 5c) to obtain a DC output voltage, and the soft Switching capacitance means (Cq1)
At least through the auxiliary winding (N3) in order to supply the auxiliary winding (N3) with a current capable of generating a voltage in the main winding (N1) for enabling the discharge of Auxiliary switch (Q2) connected in parallel to the smoothing capacitor (C1), the main switch (Q1) and the auxiliary switch (Q2)
And a first function of controlling ON / OFF of the main switch (Q1) at a repetition frequency higher than the frequency of the AC voltage applied to the AC input terminals (1, 2),
In order to soft-switch the main switch (Q1) when the main switch (Q1) is turned on, the auxiliary switch (Q2) is activated at a time point (t1) prior to the start time point (t2) of the ON control of the main switch (Q1). ) On control, and when the main switch (Q1) turns on (t5
) Or the time (t4) before the end time (t5)
A control circuit (8) having a second function of terminating the ON control of the auxiliary switch (Q2) at ~ t5). 2. The series circuit of the auxiliary winding (N3) and the auxiliary switch (Q2) is at least the main winding (N3).
2. The switching power supply device according to claim 1, wherein the switching power supply device is connected in parallel to the smoothing capacitor (C1) through a part of 1). 3. An auxiliary diode (Da) connected in series to each of the auxiliary winding (N3) and the auxiliary switch (Q2) to prevent backflow. The switching power supply device according to claim 1. 4. An auxiliary rectification output conductor (44) for outputting a rectification voltage substantially the same as the first rectification output conductor (43) from the rectification circuit (4 or 4a), and the smoothing circuit. Is electrically coupled to the main winding (N1) to obtain a voltage for charging the capacitor (C1) for the auxiliary rectifying output conductor (44) and the smoothing capacitor (C).
1) Auxiliary charging winding (N4) connected between one end and
The switching power supply device according to claim 1, further comprising: 5. An auxiliary inductor (L2) having one end connected to the auxiliary rectifying output conductor (44), the other end of the auxiliary inductor (L2) and the auxiliary charging winding (N4). A charging auxiliary capacitor (C2) connected in between, and a charging auxiliary diode (D6) connected in parallel to a series circuit of the charging auxiliary winding (N4) and the charging auxiliary capacitor (C2). 5. The switching power supply device according to claim 4, further comprising: 6. An auxiliary inductor (L2) having one end connected to the auxiliary rectification output conductor (44), the other end of the auxiliary inductor (L2) and the auxiliary charging winding (N4). A charging auxiliary diode (D6) connected in between, and a charging auxiliary capacitor (C2) connected in parallel to a series circuit of the charging auxiliary winding (N4) and the charging auxiliary diode (D6). 5. The switching power supply device according to claim 4, further comprising: 7. A backflow blocking auxiliary diode (D7) connected between the auxiliary rectifying output conductor (44) and the charging auxiliary winding (N4). The switching power supply device according to claim 4. 8. The switching power supply device according to claim 5, further comprising a reverse current blocking diode (D7) connected in series to the auxiliary inductor (L2). 9. The switching power supply device according to claim 4, further comprising a reverse current blocking diode (D5) connected in series to the main inductor (L1). 10. The rectifier circuit (4) includes a first electrode connected to the first AC input terminal (1), the first rectified output conductor (43) and an auxiliary rectified output conductor (44). A first diode (D1) having a second electrode connected respectively to the first rectified output conductor (45) and the first AC input terminal (1). A second diode (D2) having a second electrode connected to, a first electrode connected to the second AC input terminal (2), the first rectified output conductor (43), and A third diode (D3) having a second electrode respectively connected to the auxiliary rectified output conductor (44); a first electrode connected to the second rectified output conductor (45); A fourth diode having a second electrode connected to two AC input terminals (2) The switching power supply device according to claim 4, characterized in that consists of a de (D4). 11. The rectifier circuit (4) comprises a first electrode connected to the first AC input terminal (1) and a second electrode connected to the first rectified output conductor (43). A first diode (D1) having: a first electrode connected to the second rectified output conductor (45) and a second electrode connected to the first AC input terminal (1). A second diode (D2) having a first electrode connected to the second AC input terminal (2) and a second electrode connected to the first rectified output conductor (43). A third diode (D3), a first electrode connected to the second rectified output conductor (45), and a second electrode connected to the second AC input terminal (2). A fourth diode (D4), a first electrode connected to the first AC input terminal (1) and the auxiliary A fifth diode (D11) having a second electrode connected to the flow output conductor (44), a first electrode connected to the second AC input terminal (2), and the auxiliary rectification output conductor The switching power supply device according to claim 4, comprising a sixth diode (D12) having a second electrode connected to (44). 12. The main winding (N1) has a tap (10).
12. The main inductor (L1) is connected between the first rectified output conductor (43) and the tap (10), and the main inductor (L1) is connected to the tap (10). Switching power supply. 13. One end of the main inductor (L1) is connected to the first rectified output conductor (43), and the other end of the main inductor (L1) is connected to the main winding (N1) and the main switch (43). 12. The switching power supply device according to claim 1, wherein the switching power supply device is connected to an interconnection point with Q1).